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Abstract

Most image sensors are planar, opaque, and inflexible. We present a novel image sensor that is based on a luminescent concentrator (LC) film which absorbs light from a specific portion of the spectrum. The absorbed light is re-emitted at a lower frequency and transported to the edges of the LC by total internal reflection. The light transport is measured at the border of the film by line scan cameras. With these measurements, images that are focused onto the LC surface can be reconstructed. Thus, our image sensor is fully transparent, flexible, scalable and, due to its low cost, potentially disposable.

Light transport within luminescent concentrator: 1) Incident light is transmitted and not absorbed by a fluorescent molecule. 2) Emitted light is lost at the critical escape cones. 3) Light that is not reflected on the surface is absorbed, re-emitted, and transported to the edge either directly or by total internal reflection. 4) Emitted light is self-absorbed by another dye molecule.

Schema for sampling light transport as a 2D light field: (a) Photosensors (s1, s2,...,sj) located at the edges of the LC sheet that is divided into (p1, p2,..., pi) virtual pixels (from top left to bottom right). The photosensors are positioned at the bottom of the triangular aperture slits that are located along the LC edges. (b) Close-up of a triangular slit. Each photosensor measures the transported light integral at a particular angle. (c) The measurements of the photosensors at the same local position within each triangle at the same edge can be considered as the projection of light to the edge at a specific angle.

Super-resolution reconstruction steps (9 × 9 to 27 × 27 example): The upper row shows the nine low-resolution reconstructions created with the 3 × 3 shifted light-transport matrices. The center row shows the same images with the reconstructed pixels placed at the correct positions within the high-resolution image. The bottom row presents the accumulation of the center-row images from left to right. (a) The final 27 × 27 super-resolution reconstruction. (b) Best possible result: original image (d) convolved with a 3 × 3 average kernel. (c) Direct reconstruction with a single high-resolution transport matrix.

Optimizing LC sensor parameters: An aperture of width a and a distance d to the photosensors lead to the field of view α of one triangular slit. It defines the distance w that is required by the photosensors at the edge of the LC. The integration area for a single photosensor is highlighted in orange.